Regarding recent changes notification - if you have a Checkvist PRO plan, you can subscribe for the recent changes in the list, and the e-mail with notifications about changes will be sent to you. More about notifications: https://checkvist.com/auth/help#notifications

In my previous company, we had tried the Pro version, and just because of this issue, which led to a lot of data loss, CheckVist was rejected. I am a big fan, and looking forward to implement this in my new company, but wondering if this will be the bottleneck. Any updates or alternatives, or even a multiple undo.
One specific problem was one of the team members deleted multiple items, and realized it was the wrong list he was working on.

Olli, thanks for the suggestion, but the main difficulty here is a to create a living infrastructure for task history (this is a lot of work).
When to create list snapshots is a secondary question, you approach could work as well.

A middle way in case preserving entire state (including version history for task contents) is too much work: only preserve when a task was created and list order any given time. So one could roughly see which tasks existed at a point of time though the original contents of a task may have been different originally.

Yesterday, when pressing the delete key to remove a single entry from my list, the key suddenly got stuck. When I released it finally I had accidentally removed about 20 entries, some of them containing notes and sub entries. The undo function recovered only the last one, so it was a very painful data loss. So, please provide a way to (automatically) save and (manually) restore revisions.